Seismic sensor and earthquake determination method

ABSTRACT

A seismic sensor includes a measurement unit configured to measure acceleration; an earthquake determination unit configured to determine whether or not an earthquake has occurred based on the acceleration measured in a predetermined determination period; an index calculator configured to calculate an index value indicating a scale of an earthquake in an earthquake processing period after the predetermined determination period, when the earthquake determination unit determines that an earthquake has occurred; a continuous earthquake determination unit configured to determine whether or not an earthquake has occurred, based on the acceleration measured in the earthquake processing period; and a shut-off determination unit configured to inhibit output of the shut-off signal regardless of the index value when the continuous earthquake determination unit determines that no earthquake has occurred.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from U.S. patent Ser. No.16/605,749, which is a National Stage Entry of International Patent No.PCT/JP2018/009369 filed Mar. 12, 2018, which claims priority fromJapanese Patent Application No. 2017-129940 filed Jun. 30, 2017. Thecontent of both applications are incorporated herein in their entirety.

TECHNICAL FIELD

The present invention relates to a seismic sensor and an earthquakedetermination method.

BACKGROUND ART

In a case of a device that is provided in a meter box or the like and isdriven by a battery, for example, such as a seismic sensor used to shutoff gas and electricity when an earthquake occurs, it is particularlydesirable to reduce standby power. However, while a seismic sensor usinga microcontroller can obtain an index value for evaluating a scale of anearthquake through arithmetic processing, power consumption tends toincrease as compared with a mechanical seismic sensor that is energizedin response to vibration, which has been conventionally used. Inaddition, depending on an environment in which the device is installed,noise due to human-based vibration is also measured, and a degree ofmeasured noise varies. Moreover, if such noise is repeatedly detectederroneously as an earthquake, the power consumption of the seismicsensor increases.

In this regard, there is proposed a technique for improving the accuracyof determination by performing earthquake determination after shiftingfrom a power saving mode to a measurement mode, and filtering measuredacceleration in the seismic sensor that returns to the power savingmode, to remove a noise component when it is determined as not anearthquake (for example, Patent Document 1).

Processing by the seismic sensor described above is to performprocessing such as: shifting from a power saving mode to the measurementmode to perform earthquake determination when acceleration of apredetermined level or higher is detected; calculating an evaluationindex indicating a scale of the earthquake when it is determined that anearthquake has occurred, while returning to the power saving mode whenit is determined as not an earthquake; and notifying an external deviceor a related device when a scale of the earthquake is a certain level orhigher.

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: Japanese Unexamined Patent Publication No.    2017-15604

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Conventionally, the determination as to whether vibration measured bythe seismic sensor is an earthquake or noise has been made based onvibration immediately after the seismic sensor shifts from a powersaving mode to a measurement mode. However, as described above, a pulseimpact caused by daily life vibration due to human-based vibration orthe like may have been erroneously determined as an earthquake. Further,even in a case where there is such erroneous determination, if anevaluation index value indicating a scale of the earthquake is a certainvalue or more, there has been a case where a shut-off signal forshutting off energy supply such as gas or electricity is erroneouslyoutput to an external device or a related device on the assumption thata scale of the earthquake a certain level or higher.

The present invention has been made in view of the above problem, and anobject thereof is to provide a technique that can suppress erroneousdetermination of noise as an earthquake in a seismic sensor anderroneous output of a shut-off signal.

Means for Solving the Problem

A seismic sensor according to the present invention includes: ameasurement unit configured to measure acceleration;

an earthquake determination unit configured to determine whether or notan earthquake has occurred based on the acceleration measured in adetermination period that is predetermined; and

an index calculator configured to calculate an index value indicating ascale of an earthquake in an earthquake processing period after thedetermination period, when the earthquake determination unit determinesthat an earthquake has occurred.

In the seismic sensor,

in the earthquake processing period, when an index value calculated bythe index calculator is equal to or larger than a predeterminedthreshold, a shut-off signal for shutting off an operation is output toan external device or a related device provided together.

The seismic sensor further includes:

a continuous earthquake determination unit configured to determinewhether or not an earthquake has occurred, based on the accelerationmeasured in the earthquake processing period; and

a shut-off determination unit configured to inhibit output of theshut-off signal regardless of the index value, when the continuousearthquake determination unit determines that no earthquake hasoccurred.

Here, in a conventional seismic sensor, when an earthquake determinationunit determines that an earthquake has occurred, an index calculatorcalculates an index value indicating a scale of the earthquake, in anearthquake processing period after a determination period. Then, whenthe calculated index value is equal to or larger than a predeterminedthreshold, for example, a shut-off signal is output toward an externaldevice or a related device connected with the seismic sensor, and theexternal device or the related device shuts off electricity or gas basedon this signal. Whereas, in the present invention, the continuousearthquake determination unit temporarily determines that an earthquakehas occurred in the determination period for the earthquakedetermination, and continues determination as to whether or not anearthquake has occurred even after shifting to the earthquake processingperiod. Then, when the continuous earthquake determination unitdetermines that an earthquake has not occurred in the earthquakeprocessing period, the shut-off determination unit inhibits output ofthe shut-off signal regardless of the index value.

Consequently, when noise other than an earthquake is erroneouslydetermined as an earthquake in the determination period and shift ismade to the earthquake processing period, the determination as towhether or not an earthquake has occurred continues in parallel with thecalculation of the index value by the index calculator. Then, when it isdetermined that no earthquake has occurred in the earthquake processingperiod, the shut-off signal is not output regardless of the index value.As a result, it is possible to prevent output of a shut-off signal tothe external device or the related device when the seismic sensorerroneously determines noise due to other cause as an earthquake, and itis possible to more reliably prevent shutting off of an operation of therelated device. Note that the present invention may be applied to aseismic sensor that shifts from a power saving mode to a measurementmode with higher power consumption than that of the power saving modewhen acceleration measured by the measurement unit exceeds apredetermined threshold, in which the predetermined determination periodis a period after shifting to the measurement mode.

Further, in the present invention, a determination criterion in theearthquake determination unit and the continuous earthquakedetermination unit may be:

a. an acceleration value;

b. a maximum value, a minimum value, a difference between a maximumvalue and a minimum value, an average value, a sum of an average valueand a variance value, a variance value, an integrated value, a changerate, spectral intensity, and integral value, of an acceleration value;

c. a response speed value or a speed value calculated from acceleration;

d. a maximum value, a minimum value, a difference between a maximumvalue and a minimum value, an average value, a sum of an average valueand a variance value, a variance value, an integrated value, a changerate, spectral intensity, and integral value, of a response speed valueor a speed value;

e. a displacement value calculated from an acceleration value;

f. a maximum value, a minimum value, a difference between a maximumvalue and a minimum value, an average value, a sum of an average valueand a variance value, a variance value, an integrated value, a changerate, spectral intensity, and integral value, of a displacement value;

g. an SI (spectrum intensity) value calculated from acceleration;

h. a maximum value, a minimum value, a difference between a maximumvalue and a minimum value, an average value, a sum of an average valueand a variance value, a variance value, an integrated value, a changerate, spectral intensity, and integral value, of an SI (spectrumintensity) value;

i. a peak frequency;

j. a magnitude relationship in comparing values of a to i describedabove in a predetermined section with a predetermined threshold;

k. a number of consecutive times when values of a to i described aboveexceed a threshold, or a number of times when a condition is satisfiedin a specified number of times; and

l. any combination of a to k above. Note that the predetermined sectionmay be the entire section of the earthquake determination and the impactdetermination, or may be a smaller unit. Further, the predeterminedsection may be a constant value or a variation value. For example, as anexample of the variation value, a difference between acceleration valuesmay be constantly calculated, and the predetermined section may bebetween a point where + changes to − and a point where + changes to −next. Further, in addition to comparison of a threshold, thedetermination may be made based on a number of consecutive times when athreshold is exceeded, or a number of times when a condition issatisfied in a specified number of times. Alternatively, thedetermination may be made from comparison of frequency characteristicsby spectral frequency resolution such as FFT.

Further, in the present invention, the determination criterion in thecontinuous earthquake determination unit may be the same determinationcriterion as the determination criterion in the earthquake determinationunit. This enables same earthquake determination to be continued in theearthquake processing period. Further, the determination criterion inthe continuous earthquake determination unit may be differentdetermination criterion from the determination criterion in theearthquake determination unit. This enables determination with higherflexibility and higher accuracy with the combination of the earthquakedetermination unit and the continuous earthquake determination unit,such as, for example, determining that an earthquake has occurred evenin a case of an impact caused by daily life vibration in the earthquakedetermination unit just in case, while determining that the impactcaused by daily life vibration is noise and not an occurrence of anearthquake in the continuous earthquake determination unit.

Further, in the present invention, when the continuous earthquakedetermination unit determines that no earthquake has occurred, theshut-off determination unit outputs a shut-off signal in such a way thata higher-level system can recognize as the shut-off signal due to afactor other than an earthquake. Here, as a method for the higher-levelsystem to recognize as a shut-off signal due to a factor other than anearthquake, for example, the shut-off output itself may be output in apattern different from that of the shut-off output due to an earthquake,or discrimination as to whether being caused by an earthquake or not maybe made possible by reading internal information of the seismic sensor.The expression of being not an earthquake may be embodied as an impactor noise. This enables the continuous earthquake determination unit todetermine processing on the external device or related device side thathas received the shut-off signal, independently of the processing of theseismic sensor, for example, when an impact based on a predetermineddaily life vibration is detected. As a result, it is possible toconstruct processing contents with a higher flexibility as a wholesystem.

Further, the present invention may be an earthquake determination methodincluding: an earthquake determination step of determining whether ornot an earthquake has occurred based on the acceleration measured in adetermination period that is predetermined; and

an index calculation step of calculating an index value indicating ascale of an earthquake in an earthquake processing period after thedetermination period, when it is determined that an earthquake hasoccurred in the earthquake determination step.

In the earthquake determination method, when an index value calculatedin the earthquake processing period is equal to or larger than apredetermined threshold, a shut-off signal for shutting off an operationof a related device is output.

The earthquake determination method further includes: a continuousearthquake determination step of determining whether or not anearthquake has occurred, based on the acceleration measured in theearthquake processing period; and

a shut-off determination step of inhibiting output of the shut-offsignal regardless of the index value when it is determined that noearthquake has occurred in the continuous earthquake determination step.In this case, the present invention may be applied to an earthquakedetermination method in which a power saving mode is shifted to ameasurement mode with higher power consumption than that of the powersaving mode when measured acceleration exceeds a predeterminedthreshold, and the predetermined determination period is a period aftershifting to the measurement mode.

Further, the present invention may the earthquake determination methoddescribed above in which a determination criterion in the earthquakedetermination step and the continuous earthquake determination step is:

a. an acceleration value;

b. a maximum value, a minimum value, a difference between a maximumvalue and a minimum value, an average value, a sum of an average valueand a variance value, a variance value, an integrated value, a changerate, spectral intensity, and integral value, of an acceleration value;

c. a response speed value or a speed value calculated from acceleration;

d. a maximum value, a minimum value, a difference between a maximumvalue and a minimum value, an average value, a sum of an average valueand a variance value, a variance value, an integrated value, a changerate, spectral intensity, and integral value, of a response speed valueor a speed value;

e. a displacement value calculated from an acceleration value;

f. a maximum value, a minimum value, a difference between a maximumvalue and a minimum value, an average value, a sum of an average valueand a variance value, a variance value, an integrated value, a changerate, spectral intensity, and integral value, of a displacement value;

g. an SI (spectrum intensity) value calculated from acceleration;

h. a maximum value, a minimum value, a difference between a maximumvalue and a minimum value, an average value, a sum of an average valueand a variance value, a variance value, an integrated value, a changerate, spectral intensity, and integral value, of an SI (spectrumintensity) value;

i. a peak frequency;

j. a magnitude relationship in comparing values of a to i describedabove in a predetermined section with a predetermined threshold;

k. a number of consecutive times when values of a to i described aboveexceed a threshold, or a number of times when a condition is satisfiedin a specified number of times; and

l. any combination of a to k above. Here, the predetermined section maybe the entire section of the earthquake determination and the impactdetermination, or may be a smaller unit. Further, the predeterminedsection may be a constant value or a variation value. For example, as anexample of the variation value, a difference between acceleration valuesmay be constantly calculated, and the predetermined section may bebetween a point where + changes to − and a point where + changes to −next. Further, in addition to comparison of a threshold, thedetermination may be made based on a number of consecutive times when athreshold is exceeded, or a number of times when a condition issatisfied in a specified number of times. Alternatively, thedetermination may be made from comparison of frequency characteristicsby spectral frequency resolution such as FFT.

Further, the present invention may be the earthquake determinationmethod described above in which the determination criterion in thecontinuous earthquake determination step is the same as thedetermination criterion in the earthquake determination step.

Further, the present invention may be the earthquake determinationmethod described above in which, when it is determined that noearthquake has occurred in the continuous earthquake determination step,a shut-off signal is output in such a way that a higher-level system canrecognize as the shut-off signal due to a factor other than anearthquake, in the shut-off determination step. Here, as a method forthe higher-level system to recognize as a shut-off signal due to afactor other than an earthquake, for example, the shut-off output itselfmay be output in a pattern different from that of the shut-off outputdue to an earthquake, or discrimination as to whether being caused by anearthquake or not may be made possible by reading internal informationof the seismic sensor. The expression of being not an earthquake may beembodied as an impact or noise.

It should be noted that the contents described in MEANS FOR SOLVING THEPROBLEM can be combined as much as possible without departing from theproblems and technical ideas of the present invention.

Effect of the Invention

According to the above invention, it is possible to more reliablysuppress erroneous determination of noise as an earthquake in theseismic sensor and erroneous output of a shut-off signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a device configuration diagram showing an example of a seismicsensor.

FIG. 2 is a functional block diagram showing an example of the seismicsensor.

FIGS. 3A to 3C are views for explaining acceleration measured in theembodiment and thresholds.

FIG. 4 is a processing flowchart showing an example of conventionalseismic processing in the seismic sensor.

FIG. 5 is a functional block diagram of the seismic sensor according toExample 1 of the present invention.

FIG. 6 is a processing flowchart showing an example of seismicprocessing by a seismic sensor according to Example 1 of the presentinvention.

FIG. 7 is a processing flowchart showing an example of earthquakeprocessing and continuous earthquake determination processing accordingto Example 1 of the present invention.

FIGS. 8A and 8B are views showing an operation of the seismic sensoraccording to Example 1 when acceleration due to a pulse impact isdetected.

FIG. 9 is a processing flowchart showing an example of earthquakedetermination processing according to Example 2 of the presentinvention.

FIGS. 10A and 10B are views showing an operation of the seismic sensorwhen the earthquake determination processing according to Example 1 isexecuted, and when the earthquake determination processing according toExample 2 is executed, in a case where acceleration due to a pulseimpact is detected.

FIGS. 11A and 11B are views showing an operation of the seismic sensorwhen continuous earthquake determination processing according to Example1 is executed, and when the continuous earthquake determinationprocessing according to Example 2 is executed, in a case whereacceleration due to a pulse impact is detected in earthquake processing.

FIG. 12 is a view showing variations of earthquake determinationconditions in the earthquake determination processing.

FIGS. 13A and 13B are views for explaining conditions for determining asa pulse impact caused by daily life vibration in the earthquakedetermination processing.

FIG. 14 is a view for explaining earthquake determination conditions andoperations in the earthquake determination processing.

FIG. 15 is a processing flowchart showing an example of seismicprocessing in a seismic sensor in a case where a power saving mode isnot set.

FIGS. 16A and 16B are views showing an operation of the seismic sensorin the earthquake determination processing when acceleration due to apulse impact is detected in a case where the power saving mode is notset.

FIGS. 17A and 17B are views showing an operation of the seismic sensorwhen acceleration due to a pulse impact is detected in the continuousearthquake determination processing in a case where the power savingmode is not set.

MODE FOR CARRYING OUT THE INVENTION Example 1

Hereinafter, a seismic sensor according to Example 1 of the presentinvention will be described with reference to the drawings. However, theexample described below shows an example of a seismic sensor, and theseismic sensor according to the present invention is not limited to thefollowing configuration.

[Device Configuration]

FIG. 1 is a device configuration diagram showing an example of a seismicsensor according to the example. A seismic sensor 1 includes anacceleration sensor 11, a microcontroller 12, a memory 13, an outputunit 14, and an input unit 15. The acceleration sensor 11 is, forexample, an acceleration sensor using a piezoelectric element or anacceleration sensor that detects electrostatic capacity betweenelectrodes. Note that acceleration measured (also referred to as“sampled”) by the acceleration sensor 11 is output to themicrocontroller 12. The microcontroller 12 is a general-purposeintegrated circuit, for example. The microcontroller 12 acquires theacceleration measured by the acceleration sensor 11 at a predeterminedcycle, and detects an occurrence of an earthquake and calculates anindex value indicating a scale of the earthquake based on theacceleration.

Further, the microcontroller 12 operates in different forms, such as anactive mode or a sleep mode, depending on the situation. The sleep modeis an operation mode that reduces power consumption as compared with theactive mode, by the microcontroller 12 operating with limited functions,such as stopping execution of instructions while receivinginterruptions, or stopping clock supply. In the active mode, themicrocontroller 12 performs determination processing as to whetherdetected vibration is an earthquake or noise, and calculates an indexvalue indicating a scale of the earthquake.

The memory 13 is a temporary memory such as a random access memory (RAM)or a non-volatile memory such as an erasable programmable read onlymemory (EPROM), and holds, for example, measured acceleration, athreshold used for earthquake determination, and the like. Note that thememory 13 may be a memory built in the acceleration sensor 11 or themicrocontroller 12. Further, the output unit 14 is an output terminalincluded in the microcontroller 12, for example. For example, when it isdetermined that an earthquake has occurred, the microcontroller 12outputs information indicating the occurrence of the earthquake and ascale thereof to another device via the output unit 14. Further, theinput unit 15 is an input terminal included in the microcontroller 12.The microcontroller 12 may receive, for example, an operation of aswitch (not shown) or a command input from another device via the inputunit 15. Note that a high-pass filter (not shown) may be providedbetween the acceleration sensor 11 and the microcontroller 12 to removea gravity component. Further, the microcontroller 12 may handle theacceleration measured by the acceleration sensor 11 by converting intoan absolute value of the acceleration with a predetermined offset as areference.

[Function Configuration]

Next, FIG. 2 is a functional block diagram showing an example of aconventional seismic sensor 1. The seismic sensor 1 includes anacceleration measurement unit 101, an acceleration memory 102, anactivation determination unit 103, a reference value memory 104, anearthquake determination unit 105, an evaluation index calculator 106,an output unit 107, an offset adjustment unit 108, a determinationmemory 109, and a filter 110. Note that the acceleration measurementunit 101, the activation determination unit 103, the earthquakedetermination unit 105, the evaluation index calculator 106, the offsetadjustment unit 108, and the filter 110 are realized by the accelerationsensor 11 or the microcontroller 12 shown in FIG. 1 operating based on apredetermined program. Further, the acceleration memory 102, thereference value memory 104, and the determination memory 109 arerealized by the memory 13 in FIG. 1 . Note that at least the earthquakedetermination unit 105 and the evaluation index calculator 106 arerealized by the microcontroller 12 operating in the active mode.Further, the output unit 107 is realized by the microcontroller 12 andthe output unit 14 of FIG. 1 operating based on a predetermined program.

The acceleration measurement unit 101 measures acceleration at apredetermined cycle. Note that the acceleration measurement unit 101normally repeats the measurement of acceleration at a relatively lowspeed (that is, a relatively large measurement cycle). Moreover, whenperforming such low-speed sampling, the microcontroller 12 basicallyoperates in the sleep mode. Such an operation state with low powerconsumption is also referred to as “standby state” or “power savingmode”. In other words, the “standby state” is an operation state forperforming low-speed sampling. At this time, since the microcontroller12 operates in the sleep mode with limited functions, power consumptionis suppressed.

Further, when the acceleration measurement unit 101 detects vibrationlarger than a threshold preset in the reference value memory 104, theacceleration measurement unit 101 repeats the acceleration measurementat a higher speed (that is, a relatively small cycle) than that inlow-speed sampling. When performing such high-speed sampling, themicrocontroller 12 operates in the sleep mode or the active mode. Notethat, when the earthquake determination unit 105 or the evaluation indexcalculator 106 performs processing, the microcontroller 12 operates inthe active mode. An operation state during such high-speed sampling isalso referred to as “measurement mode”, and shift of the operation statefrom the power saving mode to the measurement mode is also referred toas “activation”. In other words, the “measurement mode” is an operationstate for performing high-speed sampling. At this time, themicrocontroller 12 may operate in the sleep mode with limited functions,and may also operate in the active mode enabling the operation with themaximum calculation capacity. In the measurement mode, the samplingcycle is shortened, and the microcontroller 12 switches from the sleepmode to the active mode, which increases power consumption than that inthe power saving mode.

The filter 110 performs filtering processing on an acceleration valuemeasured by the acceleration measurement unit 101, and causes theacceleration memory 102 to store the filtered acceleration. In theembodiment, the filter 110 functions as a so-called digital filter. Anexisting technique can be adopted as a specific method of the filtering.The filter 110 functions as a low-pass filter, for example, bycalculating a moving average of absolute values of acceleration.

Further, the acceleration memory 102 holds the acceleration valuemeasured by the acceleration measurement unit 101 or the accelerationvalue filtered by the filter 110. The activation determination unit 103compares the acceleration value measured by the acceleration measurementunit 101 with an activation threshold stored in the reference valuememory 104, and activates the power saving mode to the measurement modewhen the acceleration value exceeds the activation threshold. Further,the earthquake determination unit 105 uses the acceleration measured bythe acceleration measurement unit 101 in the measurement mode and athreshold preset in the reference value memory 104, to determine whetherthe measured acceleration indicates an earthquake or is noise. In theexample, the earthquake determination unit 105 defines one or aplurality of determination periods after the activation determinationunit 103 detects acceleration exceeding the activation threshold, andperforms processing for each determination period.

When the earthquake determination unit 105 determines to be anearthquake, the evaluation index calculator 106 calculates an evaluationindex indicating a scale of the earthquake. For example, an SI (spectrumintensity) value is calculated as an earthquake evaluation index. Then,the output unit 107 outputs the calculated SI value to an externaldevice. In addition, in the external device, when it is determined thatthe earthquake is of a predetermined scale or more based on the SIvalue, for example, processing of shutting off energy supply such as gasor electricity may be performed.

Whereas, when the earthquake determination unit 105 determines that thevibration is noise, the offset adjustment unit 108 performs so-calledoffset adjustment. In the example, a noise component included in ameasured acceleration, such as: a change amount in the measured valuecaused with a change of the sensor over time; a change amount in themeasured value caused with a temperature change; or a change amount inthe measured value caused with a direction change of gravitationalacceleration with respect to the sensor when a position of the installedsensor tilts for some reason, is called an offset component. The offsetadjustment unit 108 calculates, for example, a median value of maximumand minimum acceleration values determined as noise or an average valueof the acceleration, as the offset component.

FIGS. 3A to 3C are views for explaining acceleration measured in theembodiment, an offset component, and a threshold. In the graphs of FIGS.3A to 3C, a vertical axis indicates magnitude of acceleration, and ahorizontal axis indicates a lapse of time. When vibration indicated by athick solid line is measured as shown in FIG. 3A, the offset componentcan be obtained as an average value of acceleration as indicated by aone dotted chain line, for example. The calculated offset component isstored in the reference value memory 104, and used for activationdetermination executed by the activation determination unit 103, andearthquake determination executed by the earthquake determination unit105. Further, as shown in FIGS. 3B and 3C, when vibration indicated by athick solid line is measured, the threshold is defined as a valuerelative to the offset component as indicated by a broken line.

[Seismic Processing]

FIG. 4 is a processing flowchart showing an example of conventionalseismic processing by the conventional seismic sensor 1 described above.The seismic processing by the seismic sensor 1 is processing of shiftingfrom the standby state (power saving mode) to the measurement mode toperform earthquake determination processing when acceleration of apredetermined level or higher is detected, further shifting toearthquake processing when it is determined that an earthquake hasoccurred, and causing output of a shut-off signal to a related devicewhen a scale of the earthquake is a certain level or higher. Thisroutine is repeatedly and continuously executed by the seismic sensor 1.When this routine is executed, first, in S101, a threshold (referencevalue) value and the like stored in the reference value memory 104 andused for the seismic processing is initially set. When the processing ofS101 ends, the process proceeds to S102. In S102, the standby state ismaintained. More specifically, the acceleration measurement unit 101 ofthe seismic sensor 1 measures acceleration in the power saving mode. Inthe standby state, the acceleration measurement unit 101 performslow-speed sampling. When the processing of S102 ends, the processproceeds to S103. In S103, the activation determination unit 103 of theseismic sensor 1 determines whether or not to activate (that is, shiftto the measurement mode).

In this step, when the acceleration measured in S102 is equal to or lessthan the threshold (also referred to as “activation threshold”) shown inFIGS. 3A to 3C (S103:NO), the process returns to S102, to continue thestandby state (power saving mode). Here, the activation threshold is avalue representing acceleration such as 50 gal, for example, and isinitially set in S101 and held in the reference value memory 104.Whereas, when the acceleration measured in the standby state of S102 islarger than the threshold shown in FIGS. 3A to 3C (S103: YES), theacceleration measurement unit 101 shifts to the earthquake determinationprocessing (measurement mode) in S104. Note that, as shown in FIGS. 3Band 3C, the activation threshold is a relative value with the offset asa reference. Further, in the earthquake determination processing(measurement mode), the acceleration measurement unit 101 performshigh-speed sampling.

Further, in the earthquake determination processing of S104, theacceleration measurement unit 101 measures acceleration by high-speedsampling in the earthquake determination processing (measurement mode),the filter 110 performs the above-described filtering processing on themeasured acceleration, the acceleration memory 102 stores a value of theresult, and the evaluation index calculator 106 starts calculation of apredetermined evaluation index. Note that the filtering may be executedby the microcontroller 12 after shifting to the active mode, or may beexecuted by the acceleration sensor 11 while the microcontroller 12remains in the sleep mode. Note that the filtering is not essential inthe earthquake determination processing. Moreover, the processing ofS104 corresponds to a conventional earthquake determination step.

Further, at this time, as the evaluation index, for example, calculationof an SI value is started. The SI value is an example of the earthquakeevaluation index, and is a value that is recognized to be correlatedwith a degree of damage to a building. Note that the output unit 107 ofthe seismic sensor 1 outputs the calculated evaluation index to anotherdevice in a later step. Specifically, the SI value can be obtained bythe following Equation (1).

$\begin{matrix}\left\lbrack {{Formula}1} \right\rbrack &  \\{{SI} = {\frac{1}{2.4}{\int_{0.1}^{2.5}{{{Sv}\left( {T,h} \right)}{dT}}}}} & (1)\end{matrix}$The SI value described above is an index representing destructive powerof earthquake motion with an average of integral values of a speedresponse spectrum between 0.1 seconds and 2.5 seconds, which is anatural period of a highly rigid structure. Note that Sv is a speedresponse spectrum, T is a cycle, and h is an attenuation constant.

When a predetermined determination period has elapsed in the earthquakedetermination processing of S104, the process proceeds to S105. In S105,it is determined whether or not an earthquake has occurred. Morespecifically, the earthquake determination unit 105 determines whetherthe acceleration value measured in the earthquake determinationprocessing in S104 satisfies a predetermined condition. For example, theearthquake determination unit 105 determines that an earthquake hasoccurred, when a difference between a maximum value and a minimum valueof acceleration measured in the determination period is 100 gal or more.

When it is determined in S105 that an earthquake has occurred (S105:YES), the process proceeds to the earthquake processing in S107.Whereas, when it is determined in S105 that no earthquake has occurred(S105: NO), the process proceeds to offset processing in S106. In thisoffset processing, the offset adjustment unit 108 of the seismic sensor1 adjusts the above-described offset. In this step, as an offset, forexample, there is obtained an average value of the accelerationindicated by a one dotted chain line in FIG. 3A. In this way, athreshold reference is adjusted. When the processing of S106 ends, theprocess returns to the standby state of S102.

In S107, the evaluation index calculator 106 of the seismic sensor 1calculates an evaluation index indicating a scale of the earthquake.Note that, in calculating the evaluation index, the microcontroller 12operates in the active mode. The evaluation index can be calculated asthe SI value of the above-described Equation (1). Then, when theevaluation index calculated here is larger than a threshold, it isdetermined that an earthquake of an estimated strength or more hasoccurred, and the shut-off output is output to an external device (notshown) provided with the seismic sensor 1. When the processing of S107ends, the process proceeds to S108. Note that the step of calculatingthe SI value in the processing of S107 corresponds to an indexcalculation step. (This index calculation step may include a SI valuecalculation step in the earthquake determination processing.)

In S108, it is determined whether or not an earthquake processing periodhas ended. This earthquake processing period is a period that isinitially set in S101 in advance, and may be a period such as 120seconds, for example. When it is determined in S108 that the earthquakeprocessing period has not yet ended, the process returns to theprocessing before S107 to continue the earthquake processing. Whereas,when it is determined in S108 that the earthquake processing period hasended, the process proceeds to S109. In S109, the earthquake processingends, the SI value calculation also stops, and the SI value is reset.When the processing of S109 ends, the processing of this routinetemporarily ends.

However, in the conventional seismic processing as described above,since the earthquake determination is not performed in the earthquakeprocessing, there has been a case where a shut-off signal is output whenthe SI value increases due to noise, for example, even in a case wherethe determination of the earthquake determination processing has been amistake, or a case where the earthquake has been settled during theearthquake processing.

Whereas, FIG. 5 shows a functional block diagram of a seismic sensor 21in the example. The seismic sensor 21 in the example is different fromthe seismic sensor 1 shown in FIG. 2 in that the seismic sensor 21includes: a continuous earthquake determination unit 201 configured tocontinue determination as to whether acceleration is caused by anearthquake or other noise even after shifting to the earthquakeprocessing; and the shut-off determination unit 202 configured not tooutput an SI value to an external device (not shown) and to inhibitoutput of a shut-off signal to the external device when it is determinedby the continuous earthquake determination unit 201 that the vibrationis not caused by an earthquake but caused by noise, even in a case whereshift is made to seismic processing and an SI value exceeds a threshold.

FIG. 6 shows a processing flow of seismic processing by the seismicsensor 21 in the example. This routine is different from the processingflow of the seismic processing shown in FIG. 4 in that earthquakeprocessing and continuous earthquake determination processing of S117 isperformed instead of the earthquake processing of S107.

FIG. 7 shows a processing flow obtained by further disassembling theprocessing of S117. As shown in FIG. 7 , when the “earthquake processingand continuous earthquake determination processing” of S117 starts,first, in S121, an earthquake evaluation index such as an SI value bythe evaluation index calculator 106 is calculated from an accelerationvalue. Note that, in calculating the SI value, the microcontroller 12operates in the active mode and the SI value is calculated based onEquation (1). When the processing of S121 ends, the process proceeds toS122. In S122, it is determined whether or not the earthquake evaluationindex such as the SI value calculated in S120 satisfies a predeterminedthreshold. In S122, when it is determined that the earthquake evaluationindex such as the SI value is equal to or larger than the threshold, theprocess proceeds to S123 since the vibration is determined to be largerthan an estimated strength. Whereas, when it is determined that theearthquake evaluation index such as the SI value is less than thethreshold, the process proceeds to S125 since the vibration itself isdetermined to be less than the estimated strength and not so large as torequire shutting off of the related device.

In S123, it is determined again whether or not an earthquake hasoccurred as in S105. More specifically, the earthquake determinationunit 105 determines whether the acceleration value satisfies apredetermined condition. For example, the earthquake determination unit105 determines that an earthquake has occurred, when a differencebetween a maximum value and a minimum value of acceleration measured inthe determination period is 100 gal or more. In this case, thedetermination criterion in the continuous earthquake determinationprocessing is the same as the determination criterion in the earthquakedetermination processing. When it is determined in S123 that anearthquake has occurred, the process proceeds to S124. Whereas, when itis determined that no earthquake has occurred, the process proceeds toS125.

In S124, a shut-off signal is output to an external device (not shown).Whereas, no shut-off signal is output in S125. When the processing ofS124 or S125 ends, the earthquake processing and continuous earthquakedetermination processing ends, and the process proceeds to S108 of FIG.6 .

As described above, according to the example, the continuous earthquakedetermination processing continues the earthquake determination evenafter determining that an earthquake has occurred as a result of theearthquake determination processing and then shifting to the earthquakeprocessing. Then, even in a case where it is determined that theearthquake evaluation index such as the SI value is equal to or largerthan the threshold in the earthquake processing, the shut-off signal isnot output to the external device when it is determined in thecontinuous earthquake determination processing that no earthquake hasoccurred. This makes it possible to continue the earthquakedetermination over a longer period, and more reliably suppress output ofthe shut-off signal in a situation where no earthquake actually occurs.Moreover, in the earthquake processing and continuous earthquakedetermination processing in the example, when it is determined as not anearthquake, shift may be made to the standby state or to an offsetprocessing state. Alternatively, it is possible to return to theearthquake determination, continue the earthquake determination, orcontinue to perform the earthquake processing.

In Example 1 above, as an example, the earthquake determination unit 105determined that an earthquake has occurred when a difference between amaximum value and a minimum value of acceleration measured in thedetermination period is 100 gal or more. However, the determinationcriterion of the earthquake determination is not limited to the above.For example, in addition to a difference between a maximum value and aminimum value, there may be used an average value of acceleration or afilter value thereof measured during a predetermined period, a sum of anaverage value and a variance value (or standard deviation), a variancevalue, an integrated value, a change rate, a frequency, a spectrum, anintegral value, an SI value, a maximum acceleration value, a responsespeed value, a maximum speed value, and a maximum displacement amount.That is, various values corresponding to acceleration measured in eachdetermination period can be adopted. Then, it is determined as anearthquake when an obtained value and a predetermined threshold satisfya predetermined magnitude relationship.

Further, in a case of adopting a sum of an average value and a variancevalue, for example, when a standard deviation is a, a value obtained bymultiplying a by a predetermined coefficient may be handled as thevariance value. This enables suppression of activation due to noise whena noise component according to a normal distribution is detected. Notethat the integrated value may be a value obtained by addingaccelerations measured at a predetermined sampling cycle or a valueobtained by adding absolute values of accelerations. As for thefrequency, for example, it may be determined whether or not a peakfrequency is a predetermined frequency (for example, 1 Hz or the like).As for the spectrum, it may be determined as an earthquake when spectralintensity in a predetermined cycle band and a predetermined thresholdsatisfy a predetermined magnitude relationship. Further, for example,there may be used a value obtained by combining two or more of theabove-described values by addition, subtraction, division, and division.

Example 2

Next, Example 2 of the present invention will be described.

Here, in conventional earthquake determination processing performed fordetermining an occurrence of an earthquake in Example 1, even when apulse impact is detected due to human-based vibration and the likeinstead of a continuous vibration such as an earthquake, a case has beenconsidered where a shut-off signal is output as a result duringearthquake processing, on the assumption that an earthquake hasoccurred.

FIGS. 8A and 8B are views showing a response state of seismic processingto a pulse impact in Example 1. As shown in FIG. 8A, when a pulse impactis detected only once in the standby state, the process temporarilyshifts to the earthquake determination processing (measurement mode).However, the process returns to the standby state when the earthquakedetermination processing ends since it is not determined that anearthquake has occurred in the determination period in the earthquakedetermination processing. However, as shown in FIG. 8B, when a pulseimpact is detected for a plurality of times, there has been a case wherea shut-off signal is output in the earthquake processing. In otherwords, when a pulse impact is detected in the standby state, in theearthquake determination processing shifted from the standby state, andin the earthquake processing after shifting from the earthquakedetermination processing, there has been a case where that the SI valueis equal to or larger than a threshold in the earthquake processing, andthe continuous earthquake determination processing also determines thatan earthquake has occurred.

In the example, the following processing is performed such that anoccurrence of an earthquake is not erroneously determined even when apulse impact is detected for a plurality of times as described above.

The flow itself of the seismic processing in the example is the same asthe seismic processing in Example 1 shown in FIG. 6 . However, in theexample, processing contents of the earthquake determination processingS104, the determination processing S105 as to whether or not anearthquake has occurred, and the earthquake processing and continuousearthquake determination processing in S117 are different. FIG. 9 showsa detailed flow of the earthquake determination processing in theexample.

In the seismic processing in the example, when the standby state shiftsto the measurement mode and the earthquake determination processingstarts, first, the process proceeds to S210, and it is determinedwhether or not acceleration of 700 gal or more has been detected in thedetermination period. Here, when it is determined that acceleration of700 gal or more is not detected in the determination period (S210: NO),the process proceeds to S213 since the impact is determined not to bedue to daily life vibration. Whereas, when it is determined in S210 thatthe acceleration of 700 gal or more is detected in the determinationperiod, the process proceeds to S211 since it is determined that animpact due to daily life vibration may have been detected.

In S211, it is determined whether or not acceleration of ±50 gal or lesshas been detected continuously for 10 times or more, after theacceleration of 700 gal or more is detected in the determination period.Here, when it is determined that acceleration of ±50 gal or less hasbeen detected continuously for 10 times or more after the accelerationof 700 gal or more is detected (S211: YES), the process proceeds to S212since the acceleration waveform is a waveform that converges sharplyafter a large pulse of a certain level or higher, and the pulse impactis determined to be caused by daily life vibration. Whereas, when theacceleration greater than ±50 gal is detected (S211: NO) at least onceout of 10 detections after the acceleration of 700 gal or more isdetected, the process proceeds to S213 since it is not determined as apulse impact caused by daily life vibration.

In the processing of S212, a daily life vibration flag is set to T onthe premise that the acceleration detected in the determination periodis a pulse impact caused by daily life vibration. When the processing ofS212 ends, the process proceeds to S213. In S213, it is determinedwhether or not the determination period has elapsed. When it isdetermined that the determination period has not yet elapsed (S213: NO),the process returns to before the processing of S210, and the detectionof acceleration due to an earthquake/impact and the determination as towhether daily life vibration or not are continued. Whereas, when it isdetermined in S213 that the determination period has elapsed (S213:YES), the process proceeds to S214.

In S214, it is determined whether or not the daily life vibration flagis set to T. Here, when it is determined that the daily life vibrationflag is set to T (S214: YES), the process proceeds to S215 since thedetected acceleration is determined to be caused by daily lifevibration. Whereas, when it is determined that the daily life vibrationflag is not set to T (S214: NO), the process proceeds to S216 since itis determined that an earthquake may have occurred.

In S215, the SI value calculated so far is reset. When the processing ofS215 ends, the process proceeds to S217. In S216, it is determinedwhether or not a difference obtained by subtracting a minimum value froma maximum value of acceleration detected in the determination period is100 gal or more. When affirmative determination is made here, theprocess shifts to the earthquake processing since it is determined thatan earthquake has occurred. Whereas, when negative determination ismade, it is determined that no earthquake has occurred, and thus theprocess proceeds to S218, and the process returns to the initial settingprocessing after the offset processing is performed.

Further, also in S217, it is determined whether or not a differenceobtained by subtracting a minimum value from a maximum value ofacceleration detected in the determination period is 100 gal or more.Here, when affirmative determination is made, since a large accelerationhas been detected while being determined to be caused by daily lifevibration, the process returns to before the process before S210 tofurther continue the earthquake determination processing. Whereas, whennegative determination is made in S217, it is determined that noearthquake has occurred, and thus the process proceeds to S218, and theprocess returns to the initial setting processing after the offsetprocessing is performed.

FIGS. 10A and 10B show an operation when a pulse impact is repeatedlydetected in a case where the earthquake determination processing ofExample 1 is executed and a case where the earthquake determinationprocessing of this example is executed. FIG. 10A shows an operation ofthe seismic sensor when the earthquake determination processing ofExample 1 is executed, while FIG. 10B shows an operation of the seismicsensor when the earthquake determination processing of this example isexecuted. As shown in FIG. 10A, when the earthquake determinationprocessing of Example 1 is executed, shift is made to the measurementmode in response to detection of a pulse impact in the standby state,and it is determined that an earthquake has occurred in response tofurther detection of a pulse impact in the determination period. Then,since the SI value calculated in the earthquake processing exceeds athreshold, and it is determined that an earthquake has occurred also inthe continuous earthquake determination processing, there is apossibility that a shut-off signal is output.

Whereas, when the earthquake determination processing in the example isexecuted, the earthquake determination processing is repeated in aplurality of determination periods during repeated detection of pulseimpacts, and the process returns to the standby state when a pulseimpact is no longer detected.

Furthermore, as shown in FIGS. 11A and 11B, even if the process shiftsto earthquake processing, it is determined as an impact caused by dailylife vibration in the continuous earthquake determination processingwhen a pulse impact waveform is detected. Then, a shut-off signal is notoutput even if the SI value satisfies the shut-off condition, theearthquake processing is forcibly ended, and the process returns to thestandby state. Note that the continuous earthquake determination unit201 is not always necessary to return to the standby state after theshut-off determination unit 202 performs processing of inhibiting outputof the shut-off signal, but may continue the earthquake processing andcontinuous earthquake determination processing as it is. Moreover, inthe example, a process in which the continuous earthquake determinationunit 201 continues determination as to whether or not a condition of adetermination memory 109 is satisfied even after shifting to theearthquake processing, corresponds to the continuous earthquakedetermination step. In addition, a process in which, based on theearthquake evaluation index such as the SI value, the shut-offdetermination unit 202 outputs a shut-off signal when the earthquake isa certain magnitude or larger and is considered as an earthquake by thecontinuous earthquake determination unit 201, but not output theshut-off signal when the earthquake is a certain magnitude or larger andis not considered as an earthquake by the continuous earthquakedetermination unit 201, corresponds to a shut-off determination step.

Moreover, the earthquake determination processing shown in FIG. 9 hasused three conditions of (1) is the detected acceleration 700 gal ormore?(2) has acceleration of ±50 gal or less been detected continuouslyfor 10 times after acceleration of 700 gal or more has been detected?and (3) is a difference obtained by subtracting a minimum value from amaximum value of acceleration detected in a determination period 100 galor more? Then, depending on whether or not these conditions aresatisfied, it has been determined whether to continue the earthquakedetermination processing, shift to the earthquake processing, or returnto the standby process. However, the present invention is notnecessarily limited to the processing of making the above determinationusing all the conditions (1) to (3). Note that the condition of (2) hasacceleration of ±50 gal or less been detected continuously for 10 timesafter acceleration of 700 gal or more has been detected? intends todetect, as an impact, a waveform that sharply converges after a largepulse.

FIG. 12 shows variations when the determination condition in theearthquake determination processing is changed depending on whether ornot to adopt the above condition (1) is the detected acceleration 700gal or more? and on whether or not to repeat the determination period ofearthquake determination for a plurality of times. As shown below, thepresent invention is assumed to be also applicable to seismic processingin which the determination period is limited to one time, in addition tothe seismic processing on the assumption that the determination periodof earthquake determination is repeated for a plurality of times.

In a pattern of repeatedly executed determination period with thecondition of 700 gal or more, which is a pattern in the first quadrantin FIG. 12 , the pulse impact is determined to be caused by daily lifevibration in a case where, in a first determination period, a maximumacceleration of 700 gal or more is detected, a difference obtained bysubtracting a minimum value from a maximum value of accelerationdetected in the determination period is less than 100 gal, and themaximum acceleration of 700 gal or more is detected and thenacceleration of ±50 gal or less is detected continuously for 10 times ormore. Then, in a case of a pulse impact caused by daily life vibration,the earthquake determination is repeated. Further, in a case of a pulseimpact caused by daily life vibration, the SI value is reset once.

In a pattern of one time determination period with the condition of 700gal or more, which is a pattern in the second quadrant in FIG. 12 , thepulse impact is determined to be caused by daily life vibration and theprocess returns to the standby state in a case where, in the firstdetermination period, a maximum acceleration of 700 gal or more isdetected, and then acceleration of ±50 gal or less is detectedcontinuously for 10 times or more. These two conditions have priorityover the condition that a difference obtained by subtracting a minimumvalue from a maximum value of acceleration detected in the determinationperiod is less than 100 gal.

In a pattern of one time determination period without the condition of700 gal or more, which is a pattern in the third quadrant in FIG. 12 ,the pulse impact is determined to be caused by daily life vibration, andthe process returns to the standby state in a case where, in the firstdetermination period, a difference obtained by subtracting a minimumvalue from a maximum value of detected acceleration is less than 100gal, or acceleration of ±50 gal or less is detected continuously for 10times or more. However, in a case where a difference obtained bysubtracting a minimum value from a maximum value of accelerationdetected in the first determination period is less than 100 gal, andacceleration of ±50 gal or less is detected continuously for 10 times ormore, the offset value is not updated (offset processing is notperformed).

In a pattern of repeatedly executed determination period without thecondition of 700 gal or more, which is a pattern in the fourth quadrantin FIG. 12 , the pulse impact is determined to be caused by daily lifevibration in a case where, in a first determination period, a differenceobtained by subtracting a minimum value from a maximum value of detectedacceleration is less than 100 gal, and acceleration of ±50 gal or lessis detected continuously for 10 times or more. Then, in a case of apulse impact caused by daily life vibration, the earthquakedetermination is repeated. Further, in a case of a pulse impact causedby daily life vibration, the SI value is reset once.

In addition, instead of the determination conditions (1) to (3) in theearthquake determination processing in Example 2 above, as shown in FIG.13A, there may be used the two determination conditions of (4) is adifference obtained by subtracting a minimum value from a maximum valueof acceleration detected in a determination period 100 gal or more? and(5) is acceleration of 500 gal or more at a cycle of 0.04 sec or lessmade?

Further, in the above earthquake/impact process, as shown in FIG. 13B,when fixed cyclic acceleration is detected after detection of a pulseimpact, the acceleration is determined as an impact and vibration basedon daily life vibration.

As shown in FIG. 13B, in the example, for a waveform in which a fixedcyclic waveform follows after a pulse impact is detected, a case isassumed where, for example, a pulse impact occurs when human-basedvibration occurs, and then fixed frequency vibration based on a naturalfrequency of the installation environment of the seismic sensorcontinues. Further, a case is assumed where a pulse vibration isgenerated by human-based vibration in a state where a certain amount ofvibration is generated.

As shown in FIG. 14 , the determination conditions in this case are: (4)is a difference obtained by subtracting a minimum value from a maximumvalue of acceleration detected in a determination period 100 gal ormore? (6) is a difference of a difference between a maximum value and aminimum value of acceleration in the current determination period fromthat in a previous determination period >−50 gal? and (7) for a ⅓ periodof a current determination period, is a difference of a maximum valueand a minimum value of acceleration from those of a previous ⅓ period >0gal? Then, for first and second determination periods, it is determinedthat an earthquake has occurred when (4) and ((6) or (7)) are satisfied,while for the third and subsequent determination periods, it isdetermined that an earthquake has occurred when (4) and (6) aresatisfied.

Further, in this example, when a fixed cycle waveform of acceleration isdetected at the end of the determination period in which an occurrenceof an earthquake is determined, this is determined as an impact andvibration caused by daily life vibration, and the process shifts to thenext determination period. Further, when a fixed cycle waveform ofacceleration is not detected at the end of the determination period inwhich an occurrence of an earthquake is determined, the determination ofthe occurrence of an earthquake is confirmed as it is, and the processshifts to the earthquake processing.

Note that the numerical values used for the conditions of theabove-described examples are merely examples, and can be appropriatelychanged within a range consistent with the gist of the invention.

For example, the present invention is also applicable to a seismicsensor in which a power saving mode is not set. In this case, in theabove example, the process of “when processing in the power saving modeis executed and acceleration measured in the power saving mode exceeds athreshold, the power saving mode is shifted to the measurement mode” isnot necessary. FIG. 15 shows a flowchart of seismic processing in theseismic sensor in which the power saving mode is not set. In this case,as compared with the flowchart of the seismic processing shown in FIG. 6, it can be seen that the processing of S102 of maintaining the standbystate and the processing of S103 for the activation determination unit103 of the seismic sensor 1 to determine whether or not to activate areomitted. That is, in the seismic processing in FIG. 15 , the earthquakedetermination processing is always performed, and the earthquakeprocessing is interrupted, for example, when the impact is determined tobe human-based and is not an earthquake, even after it is oncedetermined in S105 that an earthquake has occurred and shift is made toearthquake processing and the continuous earthquake determinationprocessing. Here, a period of each earthquake determination may beuniform or may be changed.

Further, FIGS. 16A and 16B show an operation of the seismic sensor whena pulse impact is repeatedly detected in a case where the power savingmode is not set. FIG. 16A corresponds to an operation of the seismicsensor when the earthquake determination processing of Example 1 shownin FIG. 10A is executed, while FIG. 16B corresponds to an operation ofthe seismic sensor when the earthquake determination processing inExample 2 shown in FIG. 10B is executed. In FIGS. 16A and 16B, ascompared with the processing shown in FIGS. 10A and 10B, the processingof making an activation determination from the standby state (powersaving mode) and shifting to the earthquake determination processing(measurement mode) is omitted, and the earthquake determinationprocessing is directly performed.

In FIG. 16A, it is determined that an earthquake has occurred when apulse impact is detected in the determination period of the earthquakedetermination, and a pulse impact further detected in the determinationperiod. In this case, since the SI value calculated in the earthquakeprocessing exceeds a threshold, and it is determined that an earthquakehas occurred also in the continuous earthquake determination processing,a shut-off signal is output. Whereas, when the earthquake determinationprocessing shown in 16B is executed, the shut-off signal is not outputand the earthquake determination processing is repeated in a pluralityof determination periods during repeated detection of pulse impacts, andthe earthquake determination processing is continued even when a pulseimpact is no longer detected.

Further, FIGS. 17A and 17B show an operation of the seismic sensor whenacceleration due to a pulse impact is detected in the continuousearthquake determination processing in a case where the power savingmode is not set. This corresponds to the operation of FIGS. 11A and 11Bin a case where the power saving mode is set. In FIGS. 17A and 17B, ascompared with the processing shown in FIGS. 11A and 11B, the processingof making an activation determination from the standby state (powersaving mode) is omitted, and the earthquake determination processing isdirectly performed. In the example shown in FIG. 17A, when a pulseimpact waveform is detected in the continuous earthquake determinationprocessing, a shut-off signal may be output. Whereas, in the exampleshown in FIG. 17B, when a pulse impact waveform is detected in thecontinuous earthquake determination processing, it is determined as animpact caused by daily life vibration in the continuous earthquakedetermination processing. Then, the shut-off signal is not output evenif the SI value satisfies the shut-off condition, the earthquakeprocessing is forcibly ended, and the process returns to the earthquakedetermination processing.

DESCRIPTION OF SYMBOLS

-   -   1 seismic sensor    -   11 acceleration sensor    -   12 microcontroller    -   13 memory    -   14 output unit    -   15 input unit    -   101 acceleration measurement unit    -   102 acceleration memory    -   103 activation determination unit    -   104 reference value memory    -   105 earthquake determination unit    -   106 evaluation index calculator    -   107 output unit    -   108 offset adjustment unit    -   109 determination memory    -   110 filter    -   201 continuous earthquake determination unit    -   202 shut-off determination unit

The invention claimed is:
 1. An earthquake determination methodcomprising: shifting to a measurement mode from a standby state when anacceleration larger than a threshold is measured by a measurement unitin the standby state; calculating an index value indicating a scale ofan earthquake based on the acceleration measured in an earthquakeprocessing period starting after a predetermined period has elapsedafter shifting to the measurement mode; wherein a shut-off signal forshutting off an operation of a related device is output based on anindex value calculated in the earthquake processing period, theearthquake determination method further comprising: a continuousearthquake determination step of determining whether or not anearthquake has occurred, based on the acceleration measured in theearthquake processing period, a shut-off determination step ofinhibiting output of the shut-off signal when it is determined that noearthquake has occurred in the continuous earthquake determination step.2. The earthquake determination method according to claim 1, wherein themeasurement mode is operated in an active mode with higher powerconsumption than that of the standby state.
 3. The earthquakedetermination method according to claim 1, wherein in the standby state,the measurement of acceleration is repeated with larger cycle than thatof the measurement mode.
 4. The earthquake determination methodaccording to claim 1, wherein when a pulse impact caused by daily lifevibration is detected before the predetermined period has elapsed aftershifting to the measurement mode, output of the shut-off signal forshutting off an operation of a related device is inhibited.
 5. Theearthquake determination method according to claim 1, wherein in thecontinuous earthquake determination step, whether or not an earthquakehas occurred is determined by whether the acceleration is due to animpact caused by daily life vibration or not.
 6. The earthquakedetermination method according to claim 5, wherein when fixed cyclicacceleration is detected, the acceleration is determined as the impactbased on daily life vibration.
 7. An earthquake determination methodcomprising: shifting to a measurement mode from a standby state when anacceleration larger than a threshold is measured by a measurement unitin the standby state. calculating an index value indicating a scale ofan earthquake based on the acceleration measured in an earthquakeprocessing period starting after a predetermined period has elapsedafter shifting to the measurement mode, wherein when it is determinedthat an earthquake of a certain magnitude or larger or a vibrationlarger than an estimated strength is occurred in the earthquakeprocessing period, a shut-off signal for shutting off an operation of arelated device is output, the earthquake determination method furthercomprising: a continuous earthquake determination step of determiningwhether or not an earthquake has occurred, based on the accelerationmeasured in the earthquake processing period, a shut-off determinationstep of determining as to whether the measured acceleration is due to anearthquake or noise, and outputting the shut-off signal when it isdetermined that the earthquake has occurred, and inhibiting output ofthe shut-off signal when it is determined that the measured accelerationis due to noise.
 8. The earthquake determination method according toclaim 7, wherein the measurement mode is operated in an active mode withhigher power consumption than that of the standby state.
 9. Theearthquake determination method according to claim 7, wherein in thestandby state, the measurement of acceleration is repeated with largercycle than that of the measurement mode.
 10. The earthquakedetermination method according to claim 7, wherein when a pulse impactcaused by daily life vibration is detected before the predeterminedperiod has elapsed after shifting to the measurement mode, output of theshut-off signal for shutting off an operation of a related device isinhibited.
 11. The earthquake determination method according to claim 7,wherein in the continuous earthquake determination step, whether or notan earthquake has occurred is determined by whether the acceleration isdue to an impact caused by daily life vibration or not.
 12. Theearthquake determination method according to claim 11, wherein whenfixed cyclic acceleration is detected, the acceleration is determined asthe impact and vibration based on daily life vibration.